<![CDATA[QResource::registerResource failing]]>I am trying to load a binary resource file at runtime from an application built on Windows 10 using Qt 5.12.9. The resource file was built on Linux using Qt "rcc" tool, but using version 5.15.3.

The function QResource::registerResource() returns false using this file, which was compiled with the -binary command-line switch. After recompiling the same *.qrc file with the Windows rcc.exe of version 5.12.9, I could successfully load the file.

With earlier versions than 5.15, I never had this problem. Comparing the file sizes of the two binary files, the ones compiled with 5.15.3 on Linux are four bytes larger than the ones compiled on Windows with 5.12.9.

I haven't yet tried to load the earlier versions with the application on Linux built with 5.15. If this succeeds, then I will use those. But it seems strange that the RCC format would change between 5.12 and 5.15?

]]>https://forum.qt.io/topic/146031/qresource-registerresource-failingRSS for NodeSun, 08 Nov 2026 11:49:39 GMTTue, 27 Jun 2023 07:38:57 GMT60<![CDATA[Reply to QResource::registerResource failing on Tue, 27 Jun 2023 09:35:45 GMT]]>@Bonnie Thank you very much for your detailed reply. This was very helpful!

]]>https://forum.qt.io/post/762728https://forum.qt.io/post/762728Tue, 27 Jun 2023 09:35:45 GMT<![CDATA[Reply to QResource::registerResource failing on Tue, 27 Jun 2023 08:44:44 GMT]]>@Robert-Hairgrove I check the Qt source code of the rcc tool, apparently there does have new format from 5.12 to 5.15.
https://github.com/qt/qtbase/blob/v5.12.9/src/tools/rcc/main.cpp
https://github.com/qt/qtbase/blob/5.15/src/tools/rcc/main.cpp
The default format version of 5.12 is "2", and in 5.15 it is "3".
According to the source code, version 3 adds Zstd as the new (and default) compression algorithm, while in old version there is only zlib.
From the docs of 5.12 and 5.15:
https://doc.qt.io/archives/qt-5.12/resources.html
https://doc.qt.io/archives/qt-5.12/rcc.html
https://doc.qt.io/qt-5/resources.html
https://doc.qt.io/qt-5/rcc.html
You can see in 5.15 new arguments are added to the rcc tool such as "--compress-algo" and "--format-version".
So from my understanding 5.15 rcc should add --compress-algo zlib --format-version 2?
Not tested though :) If that do not work then maybe they are just incompatible.

[Added] found this in https://github.com/qt/qtbase/blob/dev/dist/changes-5.13.0

  • RCC now supports compressing content using the Zstandard
    (https://zstd.net) algorithm. Compared to zlib, it compresses better for
    the same CPU time, so this algorithm is the default. To go back to the
    previous algorithm, pass command-line option --compress-algo=zlib.

So this change was added from 5.13

]]>https://forum.qt.io/post/762717https://forum.qt.io/post/762717Tue, 27 Jun 2023 08:44:44 GMT<![CDATA[Reply to QResource::registerResource failing on Tue, 27 Jun 2023 07:52:37 GMT]]>Apparently, the older RCC files compiled on Windows are opened without any problems on the newer Linux Qt installation, so I will wait a few more days for more feedback and then mark this as "SOLVED"

]]>https://forum.qt.io/post/762704https://forum.qt.io/post/762704Tue, 27 Jun 2023 07:52:37 GMT